The hydroxyketones and diketones of diamondoid compounds are useful components in lubricants and traction fluids. Adamantane-2,4-dione, a diketone of the diamondoid compound adamantane, is useful not only as a component in lubricants and traction fluids, but also as an intermediate feedstock for synthesizing complex polymers. More recently, adamantane-2,4-dione has gained importance as a building block for both linear zig-zag polymers and cage structures as taught in U.S. Pat. No. 5,053,434 to Chapman, which is incorporated by reference as if set forth at length herein. The 2,4-dione has, in the past, been relatively difficult to synthesize, and this has made the 2,4-dione both costly and difficult to obtain.
The term "diamondoid compounds" is used herein in its usual sense, to designate a family of polycyclic alkanes including adamantane, diamantane, and triamantane, as well as the higher analogs and their substituted derivatives, examples of which include ethyl- and methyl-substituted diamondoids. For a survey of the chemistry of diamondoid molecules, see Fort, Raymond C., Adamantane, The Chemistry of Diamond Molecules (1976) as well as U.S. Pat. Nos. 5,019,660 to Chapman and Whitehurst and 5,053,434 to Chapman. Diamondoid feedstocks useful in the present invention may be synthesized or may be recovered from natural sources, for example, from certain natural gas deposits.
U.S. Pat. Nos. 4,952,747, 4,952,748, 4,952,749 and 4,982,049 teach methods for recovering diamondoid compounds from a natural gas stream containing the same. U.S. Pat. No. 5,019,665 teaches a method for concentrating diamondoids which are dissolved in a paraffinic solvent. U.S. Pat. No. 5,120,899 teaches a method for recovering diamondoid compounds from a natural gas stream to produce a diamondoid mixture which is substantially free of solvent contamination. The entire text of the patents cited above is incorporated herein by reference for details of diamondoid compound chemistry and production.
Previous methods for synthesizing the hydroxyketones and diketones of the diamondoid compounds (of which adamantane-2,4-dione is one example) required a rigorous intermediate product separation, for example, via column chromatography. See, for example, Gilbert, E. E. Syn. Commun., 1985, 15(1), 53-6, Faulkner, D., McKervey, M. A. J. Chem. Soc. (C) 1971, 3906-10, Henkel, J. G.; Spector, J. H. J. Org. Chem. 1983, 48, 3657-61, and Kaufmann, D.; de Meijere, A.; Luk, K.; Overton, K.; Stothers, J. Tetrahedron, 1982, 38(7), 977-989. While these techniques are effective on a bench scale, it would be desirable to avoid the intermediate product separation in general, and particularly to avoid commercial scale column chromatography. Thus the increasing demand for adamantane-2,4-dione in particular has highlighted the need for a facile, high-yield synthetic route to the diamondoid hydroxyketones and diketones which requires no column chromatography.